116 F. W. PHILLIPS — NOTES ON THE 



that it has only the histological value of a single, simple, living cell. 

 There is no special organ of circulation or respiration, no digestive 

 apparatus, there is nothing approaching to sexual elements, conju- 

 gation, or ova. 



Their reproduction, which I shall shortly touch upon, is confined 

 to the sub-division of the animal, or to its breaking up into spores. 

 I wish these unicellular characteristics to be remembered, as they 

 are necessary to a proper understanding of the group. You will of 

 course see that the Rotifera, which were formerly included in the 

 Infusoria, are now excluded by reason of their higher organization, 

 being promoted to the sub-kingdom Vermes, or the worm-tribe. 



The protoplasm or body-substance of an Infusorian may be 

 divided into two primary parts, the outer or cuticular layer which 

 is called ectoplasm, and the inner contained substance called 

 endoplasm. 



The cuticle may be again divided into two elements. Firstly, 

 an outer, structureless, hyaline layer.*' This layer is well shown in 

 the beautiful Yorticellidae or bell-animalcules, where, in addition 

 to forming the envelope of the body, it is continued downwards, as 

 the hyaline sheath of the characteristic retractile stalk. Secondly, 

 there is what is called the ciliary layer, of a hyaline appearance, 

 and of a highly elastic and contractile nature. All such appendages 

 as cilia, flagella, setae, styles, and uncini, are merely modified ex- 

 tensions or prolongations of this element. Perhaps it would be as 

 well to here explain the nature of these appendages. 



Cilia are the short, slender, vibratile appendages, which clothe 

 the entire body of some animalcules, and form the locomotive 

 organs in others. 



Flagella ai'e elongated, isolated cilia. 



Set(B are slender, hair-like, but non-vibratile appendages. 



Styles differ from the last-named organs only in their greater 

 bulk and thickness. 



Uncini coincide with styles, only they have a curved or claw-like 

 shape, and act most efficiently as ambulatory organs. 



Beneath the previously-mentioned ciliary layer there is some- 

 times found a peculiar muscular layer called by Prof. Ernst 

 Haeckel the myophan layer, but as this is found only in the higher 

 ciliate types, we shall not touch upon it, as we have now to deal 

 with the lowest section only. Whilst speaking of the ectoplasm 

 and its appendages, I ought not to omit to mention the excreted 

 elements, by which I mean all those products which are excreted 

 to form an external protective envelope for the defence of the ani- 

 malcules inclosed therein, and also the variously-modified pedicles, 

 or fulcra of attachment of the attached or sedentary species. 

 Amongst the former are included those exceedingly beautiful, 

 variable, vase-like, and tubular structures which are called lor ices. 

 These structures are the product of exudation or separation from 



* The word hynline will frequently occur ; it means a transparent structureless 

 appearance, like glass. 



